Machine tool having hydraulic feed



Dec. 8, 1931. H. ERNST ETAL 1,835,976

MACHINE TOOL H AVING HYDRAULIC FEED Original Filed Sept. 15, 1927 2 Sheets-Sheet 1 awvento'w 92W W I 331 Gum/M4 4 Z Y I Dec. 8, 1931.

H. ERNST ET AL MACHINE TOOL HAVING HYDRAULIC FEED 2 Sheets-Sheet 2 Original Filed Sept. 15, 1927 CHECK VALVE VAR/ABLE DEL/VERY METER/NG- EJCAPEMf/I/T Pl/MP.

CHECK VALVE 1.0 w PREf/YURE REL m; m L v CONTROL VAL VE w m T A ER UER H0 H CUM G0 C E o /B 2 H K R HWM anfiuaow Slime g Z Patented Dec. 1931 a UNITED STATES PATENT OFFICE HANS ERNST AND LESTER. F. NENNINGER, OF CINCINNATI, OHIO, ASSIGN'ORS TO THE CINCINNATI MILLING- MACHINE COMPANY OF CINCINNATI, OHIO, A CORPORATION OF OHIO MACHINE TOOL HAVING HYDRAULIC FEED Original application filed September 15, 1927, Serial No. 220,721. Divided and this application filed December 18, 1928.

This invention deals with machine tools and it relates more particularly to an improved hydraulic system which may be used advantageously to effect reciprocation of an element of a machine tool, such, for example; as the worktable ofa milling machine.

Hydraulic propulsions are, speaking, of two distinct types; the one now in general usage seeking to determine the rate of advance by undertaking primarily to control the flow of what may be termed the pushing oil, and the other type operating primarily to oppose the advance by a supply of oil diminished at a volumetrically uniform rate by a metering escapement.

. The latter type is fully set forth in our pending application, Serial No. 220,7 21, filed September 15, 1927, of which this appllcation is a division.

An object of this invention is to provide and embody in a machine-tool, an improyed hydraulic actuating system of the metermg escapement type and so to construct the system as to produce maximum efiiciency and smoothness of operation under varying operating conditions. In the drawings, Figure 1 is a side elevation of a milling machine embodying the present invention. Fig. 2 is a diagrammatic representation of the improved hydraulic -system.

Referring more specifically to the drawings', the milling machine illustrated in Fig. 1 comprises a base 1, column 2, over-arm 3, spindle 4 and a reciprocable work-table T, 'slidingly fitted to ways 5 and 6 provided by the base. The work-table T is the element to be translated and is shown diagrammatically in Fig. 2 as carrying a work-piece W adapted to be operated onby a cutter C. Reclprocatory motions are given to the table by means of a hydraulic motor M to which it is connected by a piston rod 7. The hydraulic motoris of conventional form comprising a cylinder 8 fixed to the machine base generally Serial No. 326,844.

and a piston 9 slidingly fitted within the cylinder and attached to the piston rod 7.

The improved hydraulic systemincludes a reservoir 10, a continuously running high .capacity low pressure pump RT adapted to draw oil from the reservoir through an inlet pipe 11, and. exhaust it through a pipe .12 forming a part of a conduit system later to be described. The oil flowing through the pipe 12 is conducted to the left end of the cylinder 8 through pipe 13; to the right end of the cylinder through pipe 14:, or to a return drain 15 extending back to the reservoir, bv the action of a control valve L. Inasmuch as the construction and operation of this valve forms no part'of this invention, a'nd as it is clearly shown and described in our prior application above referred to, and also in British Patent No. 297,104, detail illustration and description thereof in this application is deemed unnecessary. The pump RTvserves, at certain times, to deliver large, quantities of oil into the cylinder 8 to efiect rapid traverse movement of the work-table. Slow feeding movement of the work-table is effected by building up a high pressure in the cylinder 8 at one side of the piston 9 and then permitting oil to escape from the other end of the cylinder at a volumetrically uniform rate; This is effected by connecting 75 (through the action of the valve L) a booster pump B with the intake end of the cylinder and connecting a metering escapement pump Z to the other end thereof. The 'escapement pump preferably is of that type which is adapted to pass volumetrically uniform quantities of-liquid at each rotation thereof, but which may be adjusted to vary the amount of oil passed, thereby to regulate the rate at which oil is permitted to be exhausted from the exhaust end of the hydraulic motor and thereby to control the rate of feed of the Work-table. The intake end of the escapement pump is connected with the exhaust end of the hydraulic motor by aninf take pipe 16 connected with the control valve may be connected with the reservoir 10 by a. drain pipe 17 but preferably it will be con,-'

nected-with the exhaust pipe 18 of the booster pump. By so doing the oil permitted to escape from the exhaust end of the hydraulic motor is transmitted into the intake end thereof and therefore the capacity of the booster pump may be materially less than if the escapement pump exhausted into the reservoir. The booster pump may be connected with any suitable source of supply such, for example, as to the exhaust line of the constantly running rapid traverse pump RT. Any suitable means, such for example as that shown in our application hereinbefore re ferred to, may be provided to drive the pumps RT, B and Z.

To maintain a high pressure in the dis- 7 charge line 18 of the metering escapement and booster pumps and yet to afford a safety device against damage to the system in the event of abnormally high pressures therein, such as might be produced should the table come into contact with some immovable abutment, there is provided in the drain pipe 17 a high pressure relief valve 19. Likewise the rapid traverse pump RT is provided with a shunt line 20, controlled by a relief valve 21, which permits a drain back to the reservoir when the amount of oil delivered by the pump is in excess of the amount that will be taken by the system. A check valve 22, embodied in the discharge line 18, permits free flow of oil from the pumps B and Z through the pipe 18 to the motor M but precludes a reverse flow through said pipe,

should, for any reason, an abnormally high back pressure he produced in said motor, such for example, as by the action of the cutter on the work when, due to the direction of rotation of the cutter, it acts in opposition to the feed.

A second check valve 23 is embodied in the low pressure discharge line of the rapid traverse pump. This check valve permits a flow of oil from the high capacitypump to the hydraulic motor but inhibits a reversal in said flow. I I A There are occasions when the feeding of v 4 the table is resisted and the back pressure in the return line 16 may thereby fall to a low value and the metering pump Z Would not be properly fed with oil. To prevent that circumstance, a shunt line 24 extends from the outlet side ofthe rapid traverse pump line and leads to the return line 16, and in this shunt line is a check valve 25 this valve permitting no flow from the feed line to the rapid traverse line but permitting a flow in the contrary direction when the pressure in the feed line unduly diminishes.

Without further analysis, the foregoing will so fully reveal the gist of this invention that'others can by applying current knowledge, readily adapt it for Various utilizations by retaining one or more of the features that, from the standpoint of theprior art, fairly constitute essential characteristics of either the generic or specific aspects of this invention and, therefore, such adaptations should be, and are intended to be, comprehende'd within the meaning and range of through said conduit system and adapted selectively to connect the exhaust ports of either the low pressure pump or the metering and booster pumps with the intake end 0 said hydraulic motor; and a check valve in the discharge line of the low pressure high capacity pump permitting flow from said high capacity pump to said motor but inhibiting a reversal in said flow.

2. A machine tool combining a hydraulic motor; a carrier propelled thereby; a high pressure metering pump a low pressure high capacity pump; a conduit system for connecting said pumps with said motor; a booster pump; a common discharge line for said metermg pump and said booster pump; and

3. A machine tool combining a hydraulic motor; a carrier propelled thereby; a low pressure high capacity pump; a high ressure metering pump; a conduit system rom said pumps to said motor; valve means controlling the fiow of fluid through said conduit system; and a check valve arranged in a line between the discharge of the high capacity pump and the intake of the metering pump to permit flow from the former to the latter but not reversely.

4. A machine tool combining a hydraulic motor; a carrier propelled thereby; a low pressure high capacity pump; a high pressure metering pump; a booster pump; a common discharge line from said metering pump and said booster pump; a conduit system from said pumps to said motor; a check valve in the low pressure discharge line permitting flow from said high capacity pump to said motor but inhibiting a reversal in said flow; and a check valve in the discharge line from the metering and booster pumps.

5. A machine tool combining a hydraulic pressure high capacity pump; a high pressure meterlng pump; a conduit system forselectively connecting said pumps with said motor; a first check valve in the low pressure discharge line; a second check valve in the high pressure discharge line; and a check valve arranged in a line between the discharge of the high capacity pump and the intake of the metering pump to permit flow from the former to the latter but not reversely. 4

In witness whereof, we have hereunto subscribed our names.

HANS ERNST. LESTER F. NENNINGER. 

